The analysis of clinical or environmental fluid samples generally involves a series of chemical, optical, electrical, mechanical, or thermal processing steps on the samples. In recent years, there has been growing interest in developing disposable cartridges for conducting analyses of biological samples for various diagnostic and monitoring purposes. For example, U.S. Pat. No. 5,587,128 to Wilding discloses devices for amplifying a preselected polynucleotide in a sample by conducting a polynucleotide amplification reaction. U.S. Pat. No. 5,922,591 to Anderson et al. describes a miniaturized, integrated nucleic acid diagnostic device and system. The device is generally capable of performing one or more sample acquisition and preparation operations, in combination with one or more sample analysis operations.
Prior fluidic cartridges for processing fluid samples have focused on picoliter, nanoliter, and microliter sample volumes. These small sample volumes are not practical for many realistic diagnostic applications. Of special interest is the detection of target analytes (e.g., nucleic acid) that exist in low concentrations in many samples. For example, in detecting infectious diseases, gram negative bacteria can be present at less than 10 copies per milliliter of blood, cryptosporidium generally appears as only a few copies per gallon of drinking water, concentrated biothreat agents (e.g., anthrax) at less than 100 copies per milliliter of water, and food poisoning agents, such as E. coli and salmonella, may be manifested in less than 10 copies per gram of food.
The present invention provides an apparatus and method for analyzing a fluid sample to determine the presence or absence of an analyte in the sample. The apparatus includes a cartridge for separating a desired analyte from the sample and for holding the analyte for a chemical reaction and optical detection. The apparatus also includes an instrument for receiving the cartridge for sample processing. The desired analyte is typically intracellular material (e.g., nucleic acid, proteins, carbohydrates, lipids, bacteria, or intracellular parasites). In a preferred use, the analyte is nucleic acid which the cartridge separates from the fluid sample and holds for amplification (e.g., using PCR) and optical detection.
In a preferred embodiment, the cartridge has a sample port for introducing a sample into the cartridge, and a sample flow path extending from the sample port. The cartridge also has a lysing chamber in the sample flow path. The lysing chamber contains at least one filter for capturing cells or viruses from the sample as the sample flows through the lysing chamber. Beads are also disposed in the lysing chamber for rupturing the cells or viruses to release the analyte therefrom. The cartridge also includes a waste chamber in fluid communication with the lysing chamber via the sample flow path for receiving the remaining sample after the sample flows through the lysing chamber. The cartridge further includes an analyte flow path extending from the lysing chamber. The analyte flow path diverges from the sample flow path. In the preferred embodiment, the analyte flow path leads to a reaction chamber for chemically reacting and optically detecting the analyte. The cartridge also includes at least one flow controller (e.g., valves) for directing the sample into the waste chamber after the sample flows through the lysing chamber and for directing the analyte separated from the sample into the analyte flow path. The design of the cartridge permits the efficient processing of large sample volumes to enable the accurate detection of low concentration analytes.